Three superconducting stacks made of 120 REBCO coated conductor tapes were each fabricated and assembled to obtain several REBCO modules. Their levitation responses over two different permanent magnet (PM) guideways were investigated by experiment and finite element simulation. For the experiment, a test rig was developed that can measure the force in the three directions for any given relative movement between the REBCO stacks and the PM guideway. For the finite element simulation, a 2D H-formulation was adopted. To treat the high aspect ratio of REBCO tapes, an anisotropic homogenization technique was used. The agreement between the measurements and the simulations is good, thus validating the modeling methodology. It was observed from the experiment and simulation results that the perpendicular field contributes to the levitation force whereas the parallel field is responsible for the guidance force, as a result of the existence of anisotropy on the local magnetic stimulation. Based on that, promising REBCO modules including both longitudinal and transverse arrangements of REBCO stacks were proposed and tested, in terms of providing a significant levitation force with the lateral stability preserved. Moreover, a pre-load process able to suppress the relaxation of the levitation force was put forward. To conclude, this study outlines explicit principles to obtain an appropriate layout of coated conductor stacks that could be effective for practical magnetic levitation operation.

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Thermal effect will greatly affect the engineering performance of high temperature superconductors (HTSs) due to its strong dependence of electromagnetic parameters upon the local temperature. To advance the understanding of such thermal effect, a validated three-dimensional (3-D) strong-coupled electromagnetic-thermal model for HTS bulk was established in commercial finite element software COMSOL, which ensures the easy access and universality of the model. Jc(B,T) was employed to reflect both magnetic field and thermal field dependences of HTS in this model. In addition, the thermal transient equation and convective boundary condition were employed with experimentally measured HTS thermal conductivity and heat capacity to describe the thermal flux exchange between HTS and cryogenic medium. As an example of application, the established electromagnetic-thermal model was tailored to study the dynamic characteristics of a linear HTS magnetic levitation (maglev) bearing. The methodologies to numerically study the dynamic response of the linear HTS maglev bearing under free vibration state and typical operating excitations, e.g. earthquake, track irregularity and crosswind, were put forward in this paper. The influences of field cooling height, pre-load and ambient temperature, were also studied and promising methods to improve the system stability were put forward according to the obtained conclusions. The above results are reasonable and keep in concert with former experimental and theoretical studies. Moreover, some results which are inaccessible in the 2-D models, for instance, the thermal field distribution inside HTS bulk, can also be obtained due to the versatility of 3-D model. To conclude, the established HTS electromagnetic-thermal model could serve as a flexible and extensible simulation tool to study various applications of HTS bulk. Besides the application in linear HTS maglev bearing, which is systematically studied in this paper, other potential applications such as thermal analysis of HTS bulk in pulse magnetization process, HTS bulkbased electrical machines, can also be expected in future work.

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Fast radio bursts (FRBs) are extremely strong radio flares lasting several milliseconds, most of which come from unidentified objects at a cosmological distance. They can be apparently repeating or not. In this paper, we analyzed 18 repeaters and 12 non-repeating FRBs observed in the frequency bands of 400-800 MHz from Canadian Hydrogen Intensity Mapping Experiment (CHIME). We investigated the distributions of FRB isotropic-equivalent radio luminosity, considering the K correction. Statistically, the luminosity distribution can be better fitted by Gaussian form than by power-law. Based on the above results, together with the observed FRB event rate, pulse duration, and radio luminosity, FRB origin models are evaluated and constrained such that the gamma-ray bursts (GRBs) may be excluded for the non-repeaters while magnetars or neutron stars (NSs) emitting the supergiant pulses are preferred for the repeaters. We also found the necessity of a small FRB emission beaming solid angle (about 0.1 sr) from magnetars that should be considered, and/or the FRB association with soft gamma-ray repeaters (SGRs) may lie at a low probability of about 10%. Finally, we discussed the uncertainty of FRB luminosity caused by the estimation of the distance that is inferred by the simple relation between the redshift and dispersion measure (DM).

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